ROS documentation

[rland93]

I want to put some more documentation about ROS development into our documentation page.

Right now, documentation for the project is tied to main because of auto-generation of the python package documentation.

But, we will need also to document setup, installation, dependencies, and so on, of the ROS side of things.

Ultimately, I want to create an "intro to ROS" section of our documentation, that will point a new user to all of the resources they need to get a ROS environment working, install ROS/catkin/, build a workspace, etc.

I'm not going to write tutorials for all that but most people will have a hard time finding this information.

So it's a little awkward, but basically you need to have checked out main (which won't have any of the ROS code in it) to write documentation. I think this is an OK compromise, since most ROS developers will have cloned this repo into both catkin_ws and somewhere else on their PC to develop on main and ROS simultaneously.